The overall objective of this project is to continue the research into the reactivity of the microvascular bed with particular reference to the structure and function of the endothelium, the smooth muscle cells and the nerves of the component parts of the microvascular bed. A combination of intravital microscopy, microcinephotography, microiontophoresis, radioautography, and electron microscopy will be used to explore in rats and cats the microvascular responsiveness to physiological and pharmacological stimuli, as well as to pathological processes during experimental renal hypertension.